Example: Carry context across event loops

Author: Peter Giacomo Lombardo

example/carry_context.py

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+#
+# This example illustrates how to carry context from a syncronous tracing context into
+# an asynchronous one.
+#
+# In this use case, we want to launch a series of asyncronous http calls using uvloop and aiohttp
+#
+import asyncio
+import uvloop
+import aiohttp
+
+from instana.singletons import tracer, async_tracer
+
+uvloop.install()
+
+async def launch_async_calls(parent_span):
+    """
+    Method to launch a series (1 currently) of asynchronous http calls
+    using uvloop and aiohttp.  This method is run inside of an event loop
+    with `asyncio.run`, `run_until_complete` or `gather`
+    """
+
+    # Now that we are inside of the event loop, first thing to do is to initialize
+    # the tracing context using <parent_span> _and_ the asynchronous tracer <async_tracer>
+    with async_tracer.start_active_span('launch_async_calls', child_of=parent_span):
+        async with aiohttp.ClientSession() as session:
+            session.get("http://127.0.0.1/api/v2/endpoint/1")
+            session.get("http://127.0.0.1/api/v2/endpoint/2")
+            session.get("http://127.0.0.1/api/v2/endpoint/3")
+
+#
+# Synchronous application code such as from inside a Django or Flask handler
+#
+
+# Start an ENTRY span in our synchronous execution scope
+with tracer.start_active_span("launch_uvloop") as sync_scope:
+    sync_scope.span.set_tag('span.kind', 'entry')
+
+    # Launch our requests asynchronously
+    # Enter the event loop and pass in the parent tracing context (sync_scope) manually
+    asyncio.run(launch_async_calls(sync_scope.span))
+